Musicians using digital sound generating apparatus such as, for example, an electronic musical keyboard, a Prodikeys keyboard from Creative Technology Ltd, and an electronic device for generating music usually have controls which allow them to process their work product generated using the apparatus. The aforementioned apparatus have evolved to an extent whereby the work product generated using the apparatus is able to be varied significantly using the controls on the apparatus.
A headphone/earphone/speaker output for such digital sound generating apparatus is usually used solely for the purpose of reviewing the work product generated using the apparatus. The headphone/earphone/speaker output provides an output of analog signals which are not combinable with other outputs from the digital sound generating apparatus. In this regard, there has not been an output from any digital sound generating apparatus which combines output of different forms into a single output for playback/review by the musician. This may enable an alternative work product to be generated by the musician using the digital sound generating apparatus which may not have been possible otherwise. Being able to process at least one output from the digital sound generating apparatus may also allow the digital sound generating apparatus to remain usable in light of developments in digital sound processing technology. The musician may then avoid the need to constantly change the digital sound generating apparatus to cope with changes in digital sound processing technology.